This invention relates generally to the field of shock absorbers. In particular, the invention relates to fluid-damped shock absorbers.
Shock absorbers are used in a wide variety of applications. For example, shock absorbers are commonly used in vehicles, such as automobiles, trucks, motorcycles, and bicycles. Shock absorbers are also used with various industrial and engineering applications, such as with machinery, tools, trailers, lifting systems, handling systems, and the like.
One particular use of shock absorbers is with vehicle suspension systems. Such suspension systems are often designed to counter the effects of a wide variety of operating conditions. For example, such suspension systems are often designed to counter the effects created when accelerating, braking, and encountering bumps. Vehicle weight, rigidity, and the like are also factors that may be considered when designing a suspension system.
One recent trend is to use shock absorbers with bicycle suspension systems to provide a more comfortable ride and to improve the operating characteristics of the bicycle. Merely by way of example, one such suspension system is described in co-pending U.S. application Ser. No. 09/502,746, filed on the same date as the present application, the complete disclosure of which is herein incorporated herein by reference. In many bicycle suspension systems, it is important to control both compression and rebound of the shock to optimize the performance of the suspension system. Further, the vehicle may be subjected to different types of compressive forces. As such, the shock absorber may need to be designed to compensate for these various types of forces. For example, the vehicle may experience a quick jolt when encountering a bump to produce an abrupt compressive force on the shock absorber. The suspension may also experience a slower type of Compression force, such as when accelerating or climbing a steep hill.
Hence, the invention relates to shock absorbers that are useful with a variety of operating conditions. The shock absorbers of the invention may also find use with suspension systems that experience a variety of forces, including various types of compression and expansion forces.
The invention provides a fluid-damped shock absorber that comprises an outer tube having a closed end and an open end. A damper tube is disposed within the outer tube, and an inner tube is axially slidable within the outer tube. The inner tube has a closed end and an open end. A sealing piston is attached to the inner tube to provide a seal between the inside of the outer tube and the outside of the damper tube. A sealing device is attached near the open end of the outer tube to provide a seal between the outside of the inner tube and the outer tube. In this way, the inner tube may be axially translated within the outer tube as the shock absorber experiences compressive and expansive forces. As the inner tube slides within the outer tube, the inner tube slides over the damper tube.
In one embodiment, the shock absorber further includes a regulation valve that is fixed to the damper tube in a sealed arrangement with the outer tube. The regulation valve is located between the closed end of the outer tube and the sealing piston. The regulation valve is configured to regulate fluid flow of a damping fluid between the outer tube and the damper tube upon axial movement of the inner tube within the outer tube. Hence, when the shock absorber is compressed, the regulation valve regulates the flow of the damper fluid from the outer tube and into the damper tube where it flows into the inner tube. Conversely, when the shock absorber is extended, the regulation valve regulates the flow of the damper fluid from the damper tube and back into the outer tube.
Conveniently, the regulation valve may comprise an annular member having a top side, a bottom side, and at least two through holes. The regulation valve may further include a pair of washers that are coupled to the top side and the bottom side such that the damper fluid may pass through one of the through holes in one direction and through the other through hole in the other direction. In so doing, the washers regulate the amount of fluid flow through the through holes.
In one aspect, the shock absorber is configured such that the outer and the damper tube are filled with the damper fluid. Further, a compressible gas is provided within the inner tube. In this way, the pressure of the gas within the inner tube provides a biasing force to resist compression of the shock absorber. Optionally, a floating piston may be disposed within the inner tube to separate the gas from the damper fluid. A biasing member may also be disposed within the inner tube to resist movement of the floating piston toward the closed end of the inner tube. In this way, the biasing member provides an additional biasing force to resist compression of the shock absorber.
In other embodiments, the regulation valve is configured as a one-way valve to regulate the flow of the damping fluid from the damper tube and into the outer tube upon axial movement of the inner tube away from the outer tube. In this way, the regulation valve regulates the flow of the damping fluid through the shock absorber when the shock absorber is extended. Further, the outer tube includes a first orifice that is located between the regulation valve and the sealing piston and a second orifice that is located between the regulation valve and the closed end of the outer tube. A cover is disposed over the first and second orifices and is constructed to permit the flow of the damping fluid between the first and second orifices. Further, a valve shim is disposed over the first orifice. In this way, when the shock absorber is compressed, fluid within the outer tube flows around the regulation valve by passing through the first orifice, deflecting the valve shim, entering into the cover and then passing through the second orifice and back into the outer tube where the damper fluid will flow into the damper tube.
Conveniently, an adjustment mechanism may be provided to adjust the spring tension of the valve shim. In this way, the stiffness of the shock absorber may easily be adjusted. In one aspect, the adjustment mechanism comprises a rigid plate that is slidable over the valve shim to adjust the spring tension of the valve shim. Conveniently, the plate may include a rack gear, and a pinion gear may be coupled to the cover to move the plate and adjust the spring tension of the valve shim.
The shock absorbers of the invention may also include an inertia valve that permits the flow of the damper fluid from the outer tube and into the damper tube when an abrupt compressive force is applied to the shock absorber. With such embodiments, the damper tube may include a stop and an orifice that extends through a wall of the damper tube above the stop. The inertia valve is slidably mounted about the damper tube so as to be movable between a closed position where the inertia valve covers the orifice and an open position where the orifice is uncovered. A biasing mechanism is also provided to bias the inertia valve against the stop to hold the inertia valve in the closed position. When the shock absorber is abruptly compressed, the inertia valve resists any movement because of its relatively large mass. Hence, as the shock absorber compresses, the orifice moves past the inertia valve to the open position where the damper fluid may flow through the orifice and into the damper tube. If the compressive force is not sufficient to overcome the biasing force, the inertia valve remains closed. However, the regulation valve and/or the valve shim may be opened to permit the flow of damper fluid from the outer tube and into the damper tube. In this way, the shock absorber is able to accommodate different types of compressive forces.
In another aspect, a biasing system may be positioned between the sealing piston and the sealing device to bias the sealing piston away from the sealing device and create a negative biasing effect. Conveniently, the biasing system may comprise a gas that is sealed between the sealing piston and the sealing device. In still another aspect, the damper tube may be secured to the closed end of the outer tube. In such cases, the damper tube may include an orifice that extends through a wall of the damper tube at a location between the regulation valve and the closed end of the outer tube.
In another embodiment of the invention, a fluid damped shock absorber is provided. The fluid damped shock absorber has a shock absorber housing that is adapted to hold a fluid, and the housing includes a first orifice and a second orifice that extend through the housing. A cover is disposed over the first and second orifices to permit the flow of the fluid between the first and the second orifices. A valve system regulates the flow of the fluid through the orifices. The valve system comprises a valve member that is disposed over the first orifice and a rigid member that is slidable over the valve member to adjust the spring rate of the valve member.